I understand that The Hobbit frame bit is at Bilbo's party
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but again, that quote indicates that Smaug will appear in A PROLOGUE of some sort, and prologues usually occur at the beginning of a film, if I'm not mistaken.

Maybe the fireworks display will remind Bilbo of Smaug, and we will get a flashback that way. "The world is indeed full of peril, and in it there are many dark places; but still there is much that is fair; and though in all lands love is now mingled with grief, it grows perhaps the greater."-J.R.R. Tolkien